This proposal focuses on sensations arising from the lung. Sensations arising from electrical stimulation of the vagus nerve and resulting from various stimuli applied to the lungs or individual lung segments and lobes in awake humans will be examined. Sensations resulting from various stimuli applied to the lung including bronchoconstriction and localized lobar or segment lung inflation and lung collapse will be performed in normal subjects, subjects with denervated lungs (following lung transplantation) and subjects with denervated chest walls (high cervical spinal cord transection). The proposed experiments address several questions: (a) what qualities of sensations arise from pulmonary afferents, (b) which types of pulmonary afferents are responsible for various sensations, (c) are pulmonary sensations well localized to lung regions, (d) what are the perceptible thresholds of various stimuli applied to pulmonary afferents. Specifically the following will be determined: 1) what respiratory sensations arise from electrical stimulation of the vagus nerve in awake humans, 2) whether the sensations of "tightness" associated with bronchoconstriction is perceived by subjects with denervated lungs, 3) whether the sensations produced by lobar or segmented lung inflation is abolished by topical anesthesia or denervation of the lungs, 4) what sensations arise from focal collapse of lung segments. Vagal afferents are proposed to be the source of breathlessness and other respiratory sensations arising from the lung. These studies are expected to increase the understanding of the properties of respiratory sensation and improve the diagnosis and management of cardiopulmonary disease.